Conventional endoscopic procedures typically rely on the use of a flexible fiber optic tube which is inserted in the patient's body to visually examine an inner anatomical structure. The operator can then manipulate the tube inside the anatomical structure to search for any anatomical abnormalities.
Conventional colonoscopies using this procedure, although reliable, are both costly in money and time. Moreover, it is an invasive, uncomfortable and sometimes painful procedure for the patient.
Non-invasive procedures, also called virtual colonoscopies, have been used to reduce at least one of the above mentioned drawbacks of the invasive colonoscopic procedure.
These non-invasive procedures use imaging techniques such as a computed tomography (CT) scanning to obtain image data representative of the anatomical structure to analyze.
They also involve three typical patient preparation procedures: a full cathartic preparation that aims at completely cleansing the colon by using a laxative solution, a mild-laxative preparation that aims at fluidifying the colon materials and tagging any remnant solid of liquid materials, and finally a laxative-free preparation where the materials inside the colon are tagged by a solution drunk by the patient, such as a barium-based preparation.
Different automatic techniques have been proposed to locate the anatomical structure under analysis such as the colon's inner wall. However, these techniques often have difficulties to correctly locate the surface of the inner wall of the colon, especially near the interfaces between air regions and tagged regions extending therein.
In fact, if an air region-tagged region interface is not correctly identified, it may lead to leakage in the identification and location of the colon's inner wall, which is a great concern. For example, a portion of the small bowel lying proximate to the colon may be segmented and identified as a portion of the colon.
Moreover, a poor colon's inner wall segmentation may lead to over- or under-evaluation of a potential colonic lesion, which is also a great concern.
In order to reduce the above-mentioned drawbacks, dynamical algorithms using local parameters for identifying a corresponding portion of the colon's inner wall have been used.
For example, US patent application published under publication number 2008/0008367, describes a two-step segmentation method performing an initial trial segmentation enabling leakage prior to a subsequent tailored segmentation. This method however requires that the air region-tagged region interfaces be properly detected. In the case wherein an interface is too thick or inhomogeneous, the method may not properly provide a correct identification and/or location of the colon's inner wall.
Moreover, in the case the colon of the patient is collapsed due to a spasm of the patient during the image acquisition and/or the presence of an obstructive tumor, the method may not be capable of providing a correct identification of the entire colon.
It would therefore be desirable to provide an improved method for determining an estimation of a topological support of a tubular structure that will reduce at least one of the above-mentioned drawbacks.